2015 Pasture Productivity Trial

2015 Pasture Productivity Trial
Dr. Heather Darby, UVM Extension Agronomist
Abha Gupta, Lily Calderwood, Erica Cummings, Julian Post, and Sara Ziegler
UVM Extension Crops and Soils Technicians
802-524-6501
Visit us on the web: http://www.uvm.edu/extension/cropsoil
© January 2016, University of Vermont Extension
2015 PASTURE PRODUCTIVITY TRIAL
Dr. Heather Darby, University of Vermont Extension
heather.darby[at]uvm.edu
INTRODUCTION
Pasture is an essential component of feed for dairy cattle on organic farms. Productivity of pastures is
essential to ensure the cattle have a plentiful source of high quality feed during the entire grazing season.
Optimal management of pastures should include animal, plant, and soil factors. This project aims to identify
weak links in the pasture system and evaluate the impact of adopting new strategies to overcome barriers
to productivity. In this case, soil fertility and species diversity were identified as the weak links to
productivity.
The pasture where this research took place was seeded to grass about 30 years ago and prior to that had
been used for corn silage. For the last 10 years, the pasture has been minimally fertilized with a spring or
fall manure application at a rate of 3000-4000 gal ac-1. Based on soil test information, the pasture was low
in potassium (K). The pasture consisted primarily of grass with low diversity and a very low percentage of
legumes. This species scenario increases the pasture demand for nitrogen (N). The strategy to improve yield
and quality included over-seeding the pasture to improve species diversity and ultimately providing higher
yields and quality. A goal was to increase legume percentage to minimize the need for N in the pasture
system. Data was collected throughout the growing season to determine the impact on pasture productivity
and costs associated with implementation of practices.
MATERIALS AND METHODS
The trial was conducted at Holyoke Farm located in St. Albans, VT. The experimental area included 18
acres of pasture that were grazed by 60 cows using management intensive grazing techniques. General
plot management is shared in Table 1. Cows were given approximately 1 acre of pasture, representing 1
paddock, for every 24 hours that they grazed. There were two treatments that included fertility/seeding
and a control where no additional fertility or seed was applied. The fertility/seeding treatment was seeded
with a grass/legume mix, fertilized with 52 lbs ac-1 of potassium and 6.6 lbs ac-1 nitrogen.
To boost species diversity, the following forage mix was overseeded into the established pasture: 5 lbs
ac-1 each of HDR meadow fescue, Kentucky bluegrass, Preval meadow fescue, and Liherold meadow
fescue, and 2 lbs ac-1 each of TFL chicory, Freedom red clover, Dynamite red clover, Kopu white clover,
and Ladino white clover, totaling to 30 lbs ac-1. We strived to apply the seed prior to back-grazing, so the
cows would work the seed into the soil. Seed was broadcast using a nylon bag Earthway seed spreader.
Seeding occurred during the first round of grazing from 7-Jul to 2-Aug.
Based on soil test information, the soil was deficient in K and 140 lbs ac-1 per acre were recommended to
meet the needs of the pasture. To begin to rectify nutrient deficiencies 52 lbs ac-1 of potassium (100 lbs
ac-1 of potassium sulfate product) was applied to the soil. The potassium was applied after the first
grazing with a broadcast spreader. Nitrogen fertilizer was applied to help meet fertility requirements of
the pure grass stand. The paddocks were fertilized with nitrogen at 2.2 lbs ac-1 in the form of sodium
nitrate (14 lbs ac-1 of 16-0-0), 1-3 days after each grazing. The nitrogen was applied after each of three
grazing cycles, totaling to 6.6 lbs nitrogen ac-1 (42 lbs ac-1 of 16-0-0) over the course of the season. The
sodium nitrate was dissolved in water, at a ratio of one-pound fertilizer to one gallon of water, using a
paint stirrer to agitate and dissolve the fertilizer. A four wheeler with a spray tank trailer and 20 foot wide
boom was used to apply the fertilizer. GPS tracking was used to record where fertilizer had already been
sprayed and to maintain accuracy.
Table 1. General plot management, St. Albans, 2015.
Trial Information
Soil type
Previous crop
Grazing cycles
Holyoke Farm
St. Albans, VT
Massena stony loam
0-3% slope
Permanent pasture
Jul, Aug, Sep
6.6 lbs nitrogen ac-1,
applied as 42 lbs ac-1 sodium nitrate 16-0-0,
split over the three grazing cycles
Fertilizer rate
Seeding rate
Application method
52 lbs potassium ac-1,
applied as 100 lbs ac-1 potassium sulfate 0-0-52,
after the first grazing cycle
30 lbs ac-1
Four wheeler drawn spray tank with 20’ boom
Paddocks were sampled just prior to each grazing cycle to determine biomass and quality. Samples were
dried until they reached a stable weight and then sent to Dairy One Forage Laboratory for wet chemistry
analysis of crude protein (CP), net energy lactation (NEL), relative feed value (RFV), and neutral
detergent fiber (NDF). Yield was calculated from biomass samples.
The bulky characteristics of forage come from fiber. Forage feeding values are negatively associated with
fiber since the less digestible portions of plants are contained in the fiber fraction. The detergent fiber
analysis system separates forages into two parts: cell contents, which include sugars, starches, proteins,
non-protein nitrogen, fats and other highly digestible compounds; and the less digestible components
found in the fiber fraction. The total fiber content of forage is contained in the neutral detergent fiber
(NDF). This fraction includes cellulose, hemicellulose, and lignin. Because these components are
associated with the bulkiness of feeds, NDF is closely related to feed intake and rumen fill in cows.
Net energy of lactation (NEL) is calculated based on concentrations of NDF and acid detergent fiber. NEL
can be used as a tool to determine the quality of a ration. However, it should not be considered the sole
indicator of the quality of a feed as NEL is affected by the quantity of a cow’s dry matter intake, the speed
at which her ration is consumed, the contents of the ration, feeding practices, the level of her production,
and many other factors.
Variations in yield and quality can occur because of variations in genetics, soil, weather and other
growing conditions. Results were analyzed with an analysis of variance in SAS (Cary, NC). Statistical
analysis makes it possible to determine whether a difference among varieties is real, or whether it might
have occurred due to other variations in the field. At the bottom of each table, a p-value is presented for
each variable (i.e. yield). The p-value represents the probability that there was an effect from the
treatment. The lower the p-value, the greater the probability that the treatment had an effect on the
variable (i.e. yield).
RESULTS AND DISCUSSION
Seasonal precipitation and temperature were recorded with a Davis Instrument Vantage Pro2 weather
station, equipped with a WeatherLink data logger at Borderview Research Farm in Alburgh, VT. June
was a wet month with 2.73 more inches of precipitation than normal (Table 2). The remainder of
summer was relatively dry with 9.92 fewer inches of precipitation than normal over July, August, and
September. Temperature varied with May and September being much warmer than the 30 year average.
Overall, there were an accumulated 5693 GDDs this season, approximately 226 more than the historical
average.
Table 2. Seasonal weather data1 collected in Alburgh, VT, 2015.
Alburgh, VT
Average temperature (°F)
Departure from normal
May
61.9
5.5
June
63.1
-2.7
July
70.0
-0.6
August
69.7
0.9
September
65.2
4.6
October
46.5
-1.7
Precipitation (inches)
Departure from normal
1.94
-1.51
6.42
2.73
1.45
-2.70
0.00
-3.91
0.34
-3.30
2.51
-1.09
Growing Degree Days (base 32°F)
Departure from normal
930
174
938
-76
1188
-10
1184
45
1010
152
443
-59
1
Based on weather data from a Davis Instruments Vantage Pro2 with WeatherLink data logger.
Historical averages are for 30 years of NOAA data (1981-2010) from Burlington, VT.
The yield and quality of the pasture treatments are presented by grazing cycle and also averaged across
grazing cycles (Tables 3 and 4). The CP concentration did not show significant difference between
treatments when evaluating each grazing cycle and also when data was analyzed across the cycles. The
NDF concentrations, NEL, and RFV showed increasing significant difference as the season continued.
Also, when comparing NDF, NEL, and RFV across grazing cycles, the fertility/seeding treatment was
significantly better than the control. This may imply that a couple of months are needed before the quality
of pasture changes significantly, compared to not treating the pasture at all. Yield showed inconsistent
results throughout the season and showed no significant difference when comparing treatments across all
grazing cycles.
Table 3. Pasture yield and quality of the fertilizer and control treatments,
shown by each grazing cycle, 2015.
CP
NDF
NEL
% of DM
% of DM
Mcal lb-1
RFV
Yield
tons/acre
Cycle 1: 7-Jul – 2-Aug
Control
13.7
54.5
0.59
109
3388
Fertilizer
16.8
52.1
0.60
122
2859
p-value
0.46
0.78
0.83
0.61
0.55
Cycle 2: 6-Aug – 3-Sep
Control
18.3
47.3
0.65
132
3074
Fertilizer
17.2
47.6
0.64
130
2344
p-value
0.54
0.90
0.70
0.89
0.06
Cycle 3: 9-Sep – 2-Oct
Control
19.8
52.0
0.59
115
1610
Fertilizer
20.9
43.3
0.67
152
1611
p-value
0.48
0.01
0.01
0.03
0.99
Table 4. Pasture yield and quality of the fertilizer and control treatments,
shown across grazing cycles, 2015.
CP
NDF
NEL
RFV
Yield
% of DM
% of DM
Mcal lb-1
Control
18.4
50.9
0.61
119
2334
Fertilizer
18.7
46.2
0.65
138
2087
p-value
0.83
0.03
0.04
0.04
0.33
tons/acre
The total cost in time and materials to fertilize the pasture was $118 ac-1 (Table 5). The total cost in time
and materials to over-seed the pasture was $174 ac-1 (Table 6). The total cost of seeding and fertilizing
one acre was $292. However, it is key to note that seeding would not happen regularly, certain equipment
was a one-time purchase, and when activities are performed for more than one acre at a time, costs
generally go down.
Table 5. Costs associated with fertilizing pasture.
Activity/Material needed per acre
Time required (minutes)
Sodium nitrate fertilizer (14 lbs), $0.53/lb
Cost ($)
7.42
*Preparing nitrogen fertilizer solution, $12/hr
Spraying nitrogen fertilizer, $12/hr
Potassium sulfate fertilizer (100 lbs),
Spreading potassium fertilizer
Electric drill
Paint stirrer drill bit
20
20
15
4.00
4.00
55.00
3.00
40.00
5.00
118.42
Total cost to fertilize 1 acre
*Note that this cost will decrease when solution is prepared for more than one acre at a time.
Table 6. Costs associated with seeding pasture.
Activity/Material needed per acre
Seeding, $12/hr
Grass/legume seed (30 lbs)
Earthway seed spreader
Time required (minutes)
25
Total cost to seed 1 acre
Cost ($)
5.00
133.84
35.00
173.84
It is important to remember that the results here only represent one year of data at one location. The first
year of the experiment was used to primarily solidify methodology including application and sampling
techniques. The pasture was fertilized for remaining nutrient needs in the fall of 2015. Manure was
applied at 4000 gal ac-1, with nutrient analysis of 4.8% total nitrogen, 1.7% P2O5, and 5.3% K2O on a dry
weight basis. Lime was applied at 1200 lbs ac-1 to further improve pasture quality. The study will
continue in 2016 to evaluate impact of over-seeding on the species diversity and improved fertility
management on yield and quality over the entire grazing season. A return on investment will be
calculated to evaluate the strategies implemented as part of this project.
ACKNOWLEDGEMENTS
The UVM Extension Northwest Crops and Soils Team would like to thank USDA CARE Grants program
for funding this research. Special thanks to Jack and Heather Brigham and Holyoke Farm for their support
and participation. We would like to acknowledge Scott Magnan, Sara Ziegler, and Jeff Sanders for their
assistance with equipment, data collection, and data entry. This information is presented with the
understanding that no product discrimination is intended and neither endorsement of any product
mentioned, nor criticism of unnamed products, is implied.
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